In recent years, with respect to an electronic device, etc., demands for space saving of the installation place and weight reduction are increasing.
In addition, along with an increase in the localization of control mechanism or the cloud utilization, the demand for smaller size and higher performance of an electronic device is growing.
Consequently, the quantity of heat generated from the device is increased, expanding the opportunities to require excellent thermal conductivity.
For example, in the technical field of a semiconductor device used for, e.g., a high-brightness LED, a personal computer, an automotive motor control mechanism, or a device utilizing power electronic technology of converting and controlling electric power, it is strongly demanded to exhibit excellent thermal conductivity.
A molded article excellent in thermal conductivity (thermal conductive molded article) utilized for heat dissipation in the above-described field is required to have high electrical insulation, in addition to high thermal conductivity.
In a thermal conductive molded article used for this type of application, in many cases, a part or the whole thereof is often formed of a thermal conductive polymer composition containing a base polymer having electrical insulation and thermal conductive inorganic particles (hereinafter, sometimes simply referred to as “inorganic particles”) having higher thermal conductivity than the base polymer.
Among such thermal conductive polymer compositions (hereinafter, sometimes simply referred to as “polymer composition”), an epoxy resin composition employing an epoxy resin for the base polymer is excellent not only in the thermal conductivity but also in the adhesiveness, electrical insulation, strength, etc. and therefore, is extensively used.
Specifically, the epoxy resin composition is widely used in, e.g., an encapsulating material of a semiconductor device or a prepreg sheet for bonding a semiconductor device to a heat dissipater.
In the thermal conductive polymer composition, usually, as the content ratio of the inorganic particles is higher and as the thermal conductivity of the inorganic particles contained is higher, excellent thermal conductivity is exhibited.
Under such a background, attempts are being made to incorporate boron nitride particles or aluminum nitride particles, which exhibit particularly high thermal conductivity among inorganic particles, into the thermal conductive polymer composition in a high ratio.
For example, in Patent Document 1, boron nitride particles, etc. exhibiting high thermal conductivity among inorganic particles is packed in a closest packing state with an attempt to make the thermal conductivity of an epoxy resin molded article higher than ever before.